A known example of a machine tool having a table provided to be movable along a vertical Y-axis is a machine tool disclosed in Patent Literature 1 listed below. In this machine tool, a workpiece carriage and a mechanism (stand) supporting the workpiece carriage and vertically moving the workpiece carriage are disposed opposite to a machining unit including a spindle provided horizontally, with an appropriate space from the machining unit.
Further, in this machine tool, sliding rails are provided between the machining unit and the stand supporting the workpiece carriage, and roller conveyors are provided before and after the sliding rails in the longitudinal direction (conveying direction) of the sliding rails, the roller conveyor located upstream in the conveying direction loading a workpiece onto the sliding rails, and the roller conveyor located downstream in the conveying direction unloading a workpiece placed on the sliding rails.
More specifically, a workpiece is conveyed on the upstream roller conveyor and then loaded onto the sliding rails in a state of being attached to an attachment base called as “workpiece carrier”, and the workpiece carrier is held by the workpiece carriage on the sliding rails. Thereafter, the workpiece is machined by the machining unit in a state of being held by the workpiece carriage. After the machining, the workpiece carrier is released from the workpiece carriage onto the sliding rails and then unloaded onto the downstream roller conveyor.
As described above, in the machine tool disclosed in Patent Literature 1, a workpiece is conveyed in a state of being attached on the workpiece carrier. Further, the workpiece is held by the workpiece carriage and machined while remaining held by the workpiece carrier.